This study evaluated the relationship between several dimensions of parental and family religiosity with adolescent drug use behavior. Analysis was based on self-reported responses to a questionnaire administered to 1,036 undergraduate college students at Brigham Young University, of which 99.1% are members of the Church of Jesus Christ of Latter-Day Saints (LDS). About 86% reported having never used drugs. The most commonly reported reasons for abstention from drugs were that drug use violates the participants' religious beliefs and their personal moral code. In contrast, concern about legal consequences, harming family reputation, and avoiding dishonest behavior were among the least common reasons for abstaining from drugs. Children of parents who were neutral, versus critical, about religion — or who considered religion of minor importance — were more likely to have a history of drug use. Protective factors against drug behavior included also parental positions of responsibility in the church and frequent family discussions involving religion and Christian conduct. The mother's view of religion was a stronger indicator of previous drug use behavior than either the father's view of religion, positions of church responsibility held by the parents, or arguments about religious teachings with parents. Discussion on topics of Christian conduct was a stronger indicator of previous drug use behavior than were either church attendance or discussions on topics of religious doctrine.